5,173 research outputs found
Memory difference control of unknown unstable fixed points: Drifting parameter conditions and delayed measurement
Difference control schemes for controlling unstable fixed points become
important if the exact position of the fixed point is unavailable or moving due
to drifting parameters. We propose a memory difference control method for
stabilization of a priori unknown unstable fixed points by introducing a memory
term. If the amplitude of the control applied in the previous time step is
added to the present control signal, fixed points with arbitrary Lyapunov
numbers can be controlled. This method is also extended to compensate arbitrary
time steps of measurement delay. We show that our method stabilizes orbits of
the Chua circuit where ordinary difference control fails.Comment: 5 pages, 8 figures. See also chao-dyn/9810029 (Phys. Rev. E 70,
056225) and nlin.CD/0204031 (Phys. Rev. E 70, 046205
Andreev Probe of Persistent Current States in Superconducting Quantum Circuits
Using the extraordinary sensitivity of Andreev interferometers to the
superconducting phase difference associated with currents, we measure the
persistent current quantum states in superconducting loops interrupted by
Josephson junctions. Straightforward electrical resistance measurements of the
interferometers give continuous read-out of the states, allowing us to
construct the energy spectrum of the quantum circuit. The probe is estimated to
be more precise and faster than previous methods, and can measure the local
phase difference in a wide range of superconducting circuits.Comment: Changes made in light of referees comments; to appear in PR
Accounting for Slow J/psi from B Decay
A slow J/psi excess exists in the inclusive B -> J/psi+X spectrum, and is
indicative of some hadronic effect. From color octet nature of c cbar pair in
b-> c cbar s decay, one such possibility would be B -> J/psi+ K_g decay, where
K_g is a hybrid resonance with sbar g q constituents. We show that a K_g
resonance of ~ 2 GeV mass and suitably broad width could be behind the excess.Comment: 4 pages, 2 figures. To appear in Phys. Rev.
Charmless Three-Body Baryonic B Decays
Motivated by recent data on B-> p pbar K decay, we study various charmless
three-body baryonic B decay modes, including Lambda pbar pi, Sigma0 pbar pi, p
pbar pi, p pbar Kbar0, in a factorization approach. These modes have rates of
order 10^{-6}. There are two mechanisms for the baryon pair production,
current-produced and transition. The behavior of decay spectra from these
baryon production mechanisms can be understood by using QCD counting rules.
Predictions on rates and decay spectra can be checked in the near future.Comment: 26 pages, 9 figures; version to appear in Phys. Rev.
Selective laser sintering of hydroxyapatite reinforced polyethylene composites for bioactive implants and tissue scaffold development
Selective laser sintering (SLS) has been investigated for the production of bioactive implants and tissue scaffolds using composites of high-density polyethylene (HDPE) reinforced with hydroxyapatite (HA) with the aim of achieving the rapid manufacturing of customized implants. Single-layer and multilayer block specimens made of HA-HDPE composites with 30 and 40 vol % HA were sintered successfully using a CO2 laser sintering system. Laser power and scanning speed had a significant effect on the sintering behaviour. The degree of particle fusion and porosity were influenced by the laser processing parameters, hence control can be attained by varying these parameters. Moreover, the SLS processing allowed exposure of HA particles on the surface of the composites and thereby should provide bioactive products. Pores existed in the SLS-fabricated composite parts and at certain processing parameters a significant fraction of the pores were within the optimal sizes for tissue regeneration. The results indicate that the SLS technique has the potential not only to fabricate HA-HDPE composite products but also to produce appropriate features for their application as bioactive implants and tissue scaffolds
Low-Mass Baryon-Antibaryon Enhancements in B Decays
The nature of low-mass baryon-antibaryon enhancements seen in B decays is
explored. Three possibilities include (i) states near threshold as found in a
model by Nambu and Jona-Lasinio, (ii) isoscalar states with coupled to a pair of gluons, and (iii) low-mass enhancements favored by the
fragmentation process. Ways of distinguishing these mechanisms using angular
distributions and flavor symmetry are proposed.Comment: 8 pages, LaTeX, no figures, to be submitted to Phys. Rev. D. One
reference adde
SU(3) and Nonet Breaking Effects in Induced by due to Anomaly
In this paper we study the effects of on in the Standard Model. We find that this interaction can induce
new sizeable SU(3) and U(3) nonet breaking effects in
transitions and therefore in due to large matrix elements
of from QCD
anomaly. These new effects play an important role in explaining the observed
value. We also study the effects of this interaction on the contribution to
.Comment: RevTex, 12 Pages, no figures. Version to be published in PR
Hadronic B Decays to Charmed Baryons
We study exclusive B decays to final states containing a charmed baryon
within the pole model framework. Since the strong coupling for is larger than that for , the two-body charmful decay
has a rate larger than
as the former proceeds via the pole while the latter via the
pole. By the same token, the three-body decay receives less baryon-pole contribution than
. However, because the important charmed-meson
pole diagrams contribute constructively to the former and destructively to the
latter, has a rate slightly larger than
. It is found that one quarter of the rate comes from the resonant contributions. We discuss
the decays and
and stress that they are not color suppressed even though they can only proceed
via an internal W emission.Comment: 25 pages, 6 figure
MRI brain scan study of minor physical anomalies to aid the early diagnosis of autism
Poster Sessionspublished_or_final_versionThe 27th International College of Neuropsychopharmacology Congress (CINP 2010), Hong Kong, China, 6-10 June 2010. In International Journal of Neuropsychopharmacology, 2010, v. 13, suppl. S1, p. 182, abstract no. P-14.03
Phenomenological Consequences of Right-handed Down Squark Mixings
The mixings of quarks, hidden from view in Standard Model (SM), are
naturally the largest if one has an Abelian flavor symmetry. With supersymmetry
(SUSY) their effects can surface via squark loops. Squark and
gluino masses are at TeV scale, but they can still induce effects comparable to
SM in (or ) mixings, while mixing could be close to recent
hints from data. In general, CP phases would be different from SM, as may be
indicated by recent B Factory data. Presence of non-standard soft SUSY
breakings with large could enhance (or )
transitions.Comment: Version to appear in Phys. Rev. Let
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